1. Field of the Invention
This invention relates generally to an apparatus which permits replacement of a foil membrane normal to the stream of particles from a high energy particle accelerator and more particularly, but not by way of limitation, to a self contained foil changer which is hermetically sealed and permits changing of the foil without substantially disrupting the controlled environment of the accelerator.
2. History of the Prior Art
High energy particle acceleration devices such as high energy electron beam generators typically operate in a high vacuum condition and normally are connected to a target chamber by suitable propagation tubing. Since often the target chamber and associated propagation tubing are initially held at a different level of vacuum than that of the beam generator, it is necessary to provided a membrane between the beam generator and the propagation tubing to maintain the two levels of vacuum separated until firing of the generator.
The membrane also serves to separate different gas environments in the same manner. It is necessary that the membrane be of a material which will not substantially interfere with accelerated particles or electrons flowing therethrough.
Further, in the case of high energy electron beam generators, a metallic electrically conductive membrane or foil is used in a manner such that the membrane acts as the anode and is positioned adjacent the cathode of the beam generator.
Typically, the electron generator is rather massive and it may take on the order of several hours to pump down the chamber to a sufficiently high vacuum. When the generator is fired, the membrane is usually destroyed and the vacuum level in the generator and the target chamber and associated propagation tubing tend to equalize which is still normally at a rather high vacuum.
It is generally very time consuming and tedious to break the vacuum seal, disconnect the propagation tubing, replace the foil membrane and reassemble the apparatus for the next shot. Even after this is done, again, several hours may be consumed pumping the generator chamber down to the required vacuum for subsequent use.
Another problem also exists in the case of electron beam generators wherein the foil membrane is used as an anode. If the foil is not stretched tightly over the beam passageway and positioned in a plane perpendicular thereto, wrinkles in the foil may occur which can cause the beam to be deflected into the walls of the propagation tubing severely pitting the walls and resulting in destroying the tubing and often causing dangerous x-ray emission upstream of the target area.